Unsaturated hydrocarbons by oxidative dehydrogenation over ferrite catalyst



United States Patent 3,334,152 UNSATURATED HYDROCARBONS BY OXIDA- TIVE DEHYDROGENATION OVER FERRITE CATALYST Laimonis Bajars, Princeton, Maigonis Gabliks, Highland Park, and Louis J. Croce, East Brunswick, N.J., assignors to Petro-Tex Chemical Corporation, Houston, Tex., a corporation of Delaware No Drawing. Filed Jan. 2, 1964, Ser. No. 335,360 16 Claims. (Cl. 260-680) This invention relates to a process of dehydrogenating organic compounds at elevated temperatures in the presence of oxygen and particular catalysts. The catalysts of this invention are selected from the group consisting of calcium ferrite, cadmium ferrite and cobalt ferrite.

The ferrites are known commercial products which are useful, for example, in the formation of coatings suitable for high temperature applications. One method for the formation of these ferrites is by the reaction under certain conditions of iron carbonate or iron hydroxide with a carbonate of the desired metal other than iron in the presence of an atmosphere containing oxygen and a catalyst for the formation of the ferrite.

Hydrocarbons to be dehydrogenated according to the process of this invention are hydrocarbons of 4 to 7 carbon atoms and preferably are hydrocarbons selected from the group consisting of saturated hydrocarbons, monoolefins, diolefins and mixtures thereof of 4 to 5 or 6 carbon atoms having a straight chain of at least four carbon atoms and cycloaliphatics. Examples of preferred feed materials are butene-l, cis-butene-2, transbutene-Z, Z-methylbutene-l, 2-methylbutene-2, 2-methylbutene-3, n-butane, butadiene-1,3, methyl butane, cyclohexane, cyclohexene, 2-methylpentene-1, Z-methylpentene-Z and mixtures thereof. For example, n-butane may be converted to a mixture of butene-l and butene-Z or may be converted to a mixture of butene-l, butene-Z and/ or butadiene-1,3. A mixture of n-butane and butene-Z may be converted to butadiene-1,3, or to a mixture of butadiene-1,3 together with some butene-2 and butene-l. Vinyl acetylene may be present as a product, particularly when butadiene-l,3 is used as a feedstock. Thus, the process of this invention is useful in converting hydrocarbons to less saturated hydrocarbons of the same number of carbon atoms. The major proportion of the hydrocarbon converted will be to less saturated hydrocarbons of the same number of carbon atoms. Particularly the preferred products are butadiene- 1,3 and isoprene. Useful feeds may be mixed hydrocarbon streams such as refinery streams, or the olefin containing hydrocarbon mixture obtained as the product from the r dehydrogenation of hydrocarbons. In the production of gasoline from higher hydrocarbons by either thermal or catalytic cracking a hydrocarbon stream containing predominantly hydrocarbons of 4 carbon atoms may be produced and may comprise a mixture of butenes together with butadiene, butane, isobutane, isobutylene and other ingredients in minor amounts. These and other refinery by-protlucts which contain normal, ethylenically unsaturated hydrocarbons are useful as starting materials. Although various mixtures of hydrocarbons are useful, the preferred hydrocarbon feed contains at least 50 weight percent of a hydrocarbon selected from the group consisting of butene-l, butene-2, n-butane, butadiene-1,3, Z-methylbutene-l, 2-metl1ylbutene-2, 2-methylbutene-3 and mixtures thereof, and more preferably contains at least 70 weight percent, of one or more of these hydrocarbons (with both of these percentages being based on the total weight of the organic composition of the feed to the reactor). Any remainder may be, for example, essentially aliphatic hydrocarbons. This invention is particularly useful to provide a process whereby the major product of the hydrocarbon converted is a dehydrogenated hydrocarbon product having the same number of carbon atoms as the hydrocarbon fed.

Oxygen will be present in the reaction zone in an amount within the range of 0.2 to 2.5 mols of oxygen per mol of hydrocarbon to be dehydrogenated. Generally, better results may be obtained if the oxygen concentration is maintained between about 0.25 and about 1.6 mols of oxygen per mol of hydrocarbon to be dehydrogenated, such as between 0.35 and 1.2 mols of oxygen. The oxygen may be fed to the reactor as pure oxygen, as air, as oxygen-enriched air, oxygen mixed with diluents and so forth.-

Based on the total gaseous mixture entering the reactor, the oxygen ordinarily will be present in an amount from about 0.5 to 25 volume percent of the total gaseous mixture, and more usually will be present in an amount from about 1 to 15 volume percent of the total. The total amount of oxygen utilized may be introduced into the gasous mixture entering the catalytic zone or sometimes it has been found desirable to add the oxygen in increments, such as to different sections of the reactor. The above described proportions of oxygen employed are based on the total amount of oxygen used. The oxygen may be added directly to the reactor or it may be premixed, for example with a diluent or steam.

The temperature for the dehydrogenation reaction will be greater than 250 C., such as greater than about 300 C. or 375 C., and the maximum temperature in the reactor may be about 650 C. or 750 C. or perhaps higher under certain circumstances. However, excellent results are obtained within the range of or about 300 C. to 575 C. such as from or about 325 C. to or about 525 C. The temperatures are measured at the maximum temperature in the reactor. An advantage of this invention is that lower temperatures of dehydrogenation may be utilized than are possible in conventional dehydrogenation processes. Another advantage is that large quantities of heat do not have to be added to the reaction as was previously required.

The dehydrogenation reaction may be carried out at atmospheric pressure, superatrnospheric pressure or at subatmospheric pressure. The total pressure of the system will normally be about or in excess of atmospheric pressure, although sub-atmospheric pressure may also desirably be used. Generally, the total pressure will be between about 4 p.s.i.a. and about or p.s.i.a. Preferably the total pressure will be less than about 75 p.s.i.a. and excellent results are obtained at about atmospheric pressure.

The initial partial pressure of the hydrocarbon to be dehydrogenated will be equivalent to less than one-half atmosphere at a total pressure of one atmosphere. Generally the combined partial pressure of the hydrocarbon to be dehydrogenated together with the oxygen will also be equivalent to less than one-half atmosphere at a total pressure of one atmosphere. Preferably, the initial partial pressure of the hydrocarbon to be dehydrogenated will be equivalent to no greater than one-third atmosphere or no greater than one-fifth atmosphere at a total pressure of one atmosphere. Also, preferably, the initial partial pressure of the combined hydrocarbon to be dehydrogenated plus the oxygen will be equivalent to no greater than onethird or no greater than one-fifth atmosphere at a total pressure of one atmosphere. Reference to the initial partial pressure of the hydrocarbon to be dehydrogenated means the partial pressure of the hydrocarbon as it first contacts the catalytic particles. An equivalent partial pressure at a total pressure of one atmosphere means that one atmosphere total pressure is a reference point and does not imply that the total pressure of the reaction must be operated at atmospheric pressure. For example, in a mixture of one mol of butene, three mols of steam, and

one mol of oxygen under a total pressure of one atmosphere, the butene would have an absolute pressure of onefifth of the total pressure, or roughly six inches of mercury absolute pressure. Equivalent to this six inches of mercury butent absolute pressure at atmospheric pressure would be butene mixed with oxygen under a vacuum such that the partial pressure of the butene is 6 inches of mercury absolute. The combination of a diluent such as nitrogen, together with the use of a vacuum may be uti lized to achieve the desired partial pressure of the hydrocarbon. For the purpose of this invention, also equivalent to the six inches of mercury butene absolute pressure at atmospheric pressure would be the same mixture of one mol of butene, three mols of steam and one mol of oxygen under a total pressure greater than atmospheric, for example, a total pressure of p.s.i.a. Thus, when the total pressure in the reaction zone is greater than one atmosphere, the absolute values for the pressure of the hydrocarbon to be dehydrogenated will be increased in direct proportion to the increase in total pressure above one atmosphere.

The partial pressures described above may be maintained by the use of diluents such as nitrogen, helium or other gases. Conveniently, the oxygen may be added as air with the nitrogen acting as a diluent for the system. Mixtures of diluents may be employed. Volatile cornpounds which are not dehydrogenated or which are dehydrogenated only to a limited extent may be present as diluents.

Preferably the reaction mixture contains a quantity of stream, with the range generally being between about 2 and 40 rnols of stream per mol of hydrocarbon to be dehydrogenated. Preferably steam will be present in an amount from about 3 to 35 mols per mol of hydrocarbon to be dehydrogenated and excellent results have been obtained within the range of about 5 to about 30 mols of steam per mol of hydrocarbon to be dehydrogenated. The functions of the steam are several-fold, and the steam does not merely act as a diluent. Diluents generally may be used in the same quantities as specified for the steam. Excellent results are obtained when the gaseous composition fed to the reactor consists essentially of hydrocarbons, inert diluents and oxygen as the sole oxidizing agent.

The gaseous reactants may be conducted through the reaction chamber at a fairly wide range of flow rates. The optimum flow rate will be dependent upon such variables as the temperature of reaction, pressure, particle size, and whether a fluid bed or fixed bed reactor is utilized. Desirable flow rates may be established by one skilled in the art. Generally, the How rates will be within the range of about 0.10 to liquid volumes of the hydrocarbon to be dehydrogenated per volume of reactor containing catalyst per hour (referred to as LHSV), wherein the volumes of hydrocarbon are calculated at standard conditions of 25 C. and 760 mm. of mercury. Usually, the LHSV will be between 0.15 and about 5 or 10. For calculation, the volume of reactor containing catalyst is that volume of reactor space excluding the volume displaced by the catalyst. For example, if a reactor has a particular volume of cubic feet of void space, when that void space is filled with catalyst particles, the original void space is the volume of reactor containing catalyst for the purpose of calculating the flow rate. The gaseous hourly space velocity (GHSV) is the volume of the hydrocarbon to be dehydrogenated in the form of vapor calculated under standard conditions of 25 C. and 760 mm. of mercury per volume of reactor space containing catalyst per hour. Generally, the GHSV will be between about 25 and 6400, and excellent results have been obtained between about 38 and 3800. Suitable contact times are, for example, from about 0.001 or higher to about 5 or 10 seconds, with particularly good results being obtained between 0.01 and 3 seconds. The contact time is the calculated dwell time of the reaction mixture in the reaction zone, assuming the mols of product mixture are equivalent to the mols of feed mixture. For the purpose of calculation of residence times, the reaction zone is the portion of the reactor containing catalyst.

The catalytic surface described is the surface which is exposed in the dehydrogenation zone to the reactor, that is, if a catalyst carrier is used, the composition described as a catalyst refers to the composition of the surface and not to the total composition of the surface coating plus carrier. Catalyst binding agents or fillers may be used, but these will not ordinarily exceed about percent or percent by weight of the catalytic surface. These binding agents and fillers will preferably be essentially inert. Suitable catalysts are those which do not contain sodium or potassium as an additive, such as those containing less than 5 or less than 2 percent by weight of sodium or potassium based on the total weight of the catalyst. The catalyst will by definition be present in a catalytic amount. Generally the ferrite selected from the group consisting of calcium ferrite, cadmium ferrite and cobalt ferrite together with any iron and the atoms selected from the group consisting of calcium, cadmium and cobalt not combined as the ferrite will be the main active constituents. The amount of catalyst will ordinarily be present in an amount greater than 10 square feet of catalyst surface per cubic foot of reaction zone containing catalyst. Of course, the amount of catalyst may be much greater, particularly when irregular surface catalysts are used. When the catalyst is in the form of particles, either supported or unsupported, the amount of catalyst surface may be expressed in terms of the surface area per unit weight of any particular volume of catalyst particles. The ratio of catalytic surface to weight will be dependent upon various factors, including the particle size, particle size distribution, apparent bulk density of the particles, amount of active catalyst coated on the carrier, density of the carrier, and so forth. Typical values for the surface to weight ratio are such as about one-half to 200 square meters per gram, although higher and lower values may be used.

The dehydrogenation reactor may be of the fixed bed or fluid bed type. Conventional reactors for the production of unsaturated hydrocarbons are satisfactory. Excellent results have been obtained by packing the reactor with catalyst particles as the method of introducing the catalytic surface. The catalytic surface may be introduced as such or it may be deposited on a carrier by methods known in the art such as by preparing an aqueous solution or dispersion of a catalytic material and mixing the carrier with the solution or dispersion until the active ingredients are coated on the carrier. If a carrier is utilized, very useful carriers are silicon carbide, pumice and the like. When carriers are used, the amount of catalyst on the carrier will generally be between about 5 to 75 weight percent of the total weight of the active catalytic material plus carrier. Another method for introducing the required surface is to utilize as a reactor a small diameter tube wherein the tube wall is catalytic or is coated with catalytic material. Other methods may be utilized to introduce the catalytic surface such as by the use of rods, wires, mesh, or shreds and the like of catalytic material.

According to this invention, the catalyst is autoregenerative and the process is continuous. Moreover, small amounts of tars and polymers are formed as compared to some prior art processes.

The catalysts are not limited to those illustrated in the examples. Other methods of preparation and other compositions may be employed. Valuable catalysts were produced comprising as the main active constituents in the catalytic surface exposed to the reaction gases iron, oxygen and an element from the group consisting of calcium, cadmium and cobalt. The best results are obtained with catalysts having iron as the predominant metal in the catalytic surface. Preferably at least about 55 and generally at least about weight percent of the atoms of iron and the second metal will be present as the ferrite. The

catalysts will have iron in the catalytic surface in an amount of from 30 to 90 and preferably from 50 to 85 or 55 to 81 weight percent of the total weight of iron and the second metal. The preferred ferrites are the ferrites having a cubic face-centered structure. Ordinarily the ferrites will not be present in the most highly oriented crystalline structure, because it has been found that superior results may be obtained with catalysts wherein the ferrites are relatively disordered. The desired catalysts may be obtained by conducting the reaction to form the ferrite at relatively low temperatures, that is, at temperatures lower than some of the very high temperatures used for the formation of ferrites prepared for semi-conductor applications. Generally the temperature of reaction for the formation of the catalysts comprising the particular ferrites'will be less than 1300 C. and preferably less than 1150 C. The reaction time at the elevated temperature in the formation of the catalysts may preferably be from about 5 minutes to 4 hours at elevated temperatures high enough to cause formation of the ferrite but less than about 1150 C. Any iron not present in the form of the ferrite will desirably be present predominantly as gamma iron oxide. The alpha iron oxide will preferably be present in an amount of no greater than 40 weight percent of the catalytic surface, such as no greater than about 30 weight percent.

Some improvement in catalytic activity may be obtained by reducing the catalyst of the invention. The reduction of the catalyst may be accomplished prior to the initial dehydrogenation, or the catalyst may be reduced after the catalyst has been used. It has been found that a used catalyst may be regenerated by reduction and, thus, even longer catalyst life obtained. The reduction may be accomplished with any effective reducing gas such as hydrogen, carbon monoxide or hydrocarbons. Generally the flow of oxygen will be stopped during the reduction step. The temperature of reduction may be varied but the process is most economical at temperatures of at least about 200 C., with the upper limit being about 750 C. or 900 C. or even higher under certain conditions.

It is one of the advantages of this invention that halogen may also be added to the reaction gases to give excellent results. The addition of halogen to the feed is particularly effective when the hydrocarbon to be dehydrogenated is saturated. The halogen fed to the dehydrogenation zone may be either elemental halogen or any compound of halogen which would liberate halogen under the conditions of reaction. Suitable sources of halogen are such as hydrogen iodide, hydrogen bromide and hydrogen chloride; aliphatic halides such as ethyl iodide, methyl bromide, 1,2-dibromo ethane, ethyl bromide, amyl bromide and allyl bromide; cycloaliphatic halides such as cyclohexylbromide; aromatic halides such as benzyl bromide; halohydrins such as ethylene brornohydrin; halogen substituted aliphatic acids such as bromoacetic acid; ammonium iodide; ammonium bromide; ammonium chloride; organic amine halide salts such as methyl amine hydrobromide; and the like. Mixtures of various sources of halogen may be used. The prefer-red sources of halogen are iodine, bromine and chlorine and compounds thereof such as hydrogen bromide, hydrogen iodide, hydrogen chloride, ammonium bromide, ammonium iodide, ammonium chloride, alkyl halides of one to six carbon atoms and mixtures thereof, with the iodine and bromine compounds being particularly preferred, and the best results having been obtained with ammonium iodide, bromide or chloride. When terms such as halogen liberating materials or halogen materials are used in the specification and claims, this includes any source of halogen such as elemental halogen-s, hydrogen halides or ammonium halides. The amount of halogen, calculated as elemental halogen, may be as little as about 0.0001 or less mol of halogen per mol of the hydrocarbon compound to be dehydrogenated to as high as 0.2 or 0.5. The preferred described range is from about 0.001 to 0.09 mol of halogen per mol of the hydrocarbon to be dehydrogenated.

In the following examples will be found specific embodiments of the invention and details employed in the practice of the invention. Percent conversion refers to the mols of hydrocarbon consumed, based on the mols of hydrocarbon fed to the reactor, percent selectivity refers to the mols of product formed based on the mols of hydrocarbon consumed, and percent yield refers to the mols of product formed based on the mols of hydrocarbon fed.

Example 1 A cadmium ferrite catalyst was formed as follows: 64.2 grams of cadmium oxide, 79.9 grams of ferric oxide and 74.6 grams of potassium chloride were thoroughly mixed in dry form. The mixture was then reacted in a furnace at 900 C. for a period of three hours. After cooling to room temperature, hot distilled water was used to extract the potassium chloride from the reacted mixture until the extract was free of chloride ion. A reddish brown cadmium ferrite solid was obtained.

The cadmium ferrite catalyst was slurried in distilled water, dried and the dried cake broken into particles. A 6 to 8 mesh fraction was used as the catalyst. Butene-Z was dehydrogeneated at atmospheric pressure in a Vycor glass reactor (36" x 1' OD.) having a 50 cc. catalyst bed supported on a 1" deep layer of /4" x A" OD. Vycor raschig rings. Butene-2, oxygen and steam and HBr were introduced into an adapter located on top of the glass reactor, and the efiluent gases were passed through a cold-water condenser to remove most of the steam. Samples of the effiuent gases were withdrawn with a syringe at the exit from the condenser. They were analyzed in a vapor chromatograph. The butene-2 used was C.P. grade, 99.0 mol percent minimum; the oxygen was commercial grade, purity 99.5 plus, and steam was generated from the distilled water.

A mixture of butene-2, oxygen, HBr and steam was fed to the reactor in an amount of 0.85 mol of oxygen, 20 mols of steam and 0.03 mol of bromine per mol of butene-2 (calculated as Br The LHSV was 0.6. At a maximum temperature in the reactor of 650 C. butadiene-1,3 was obtained at a selectivity of greater than mol percent.

Example 2 Calcium ferrite was formed according to the method in Gmelin Handbuck der Anorganischen Chemie, 59 B45, page 1071. Ferric oxide was used as a source of iron and the atomic ratio of the. atoms of Fe to the atoms of Ca was 2 to 1. The temperature of reaction to form the ferrite was 1000 C. for a period of one hour. The calcium ferrite obtained was a slightly magnetic dark brown solid. The calcium ferrite was slurried in water to make a paste, dried, and the dried cake broken into lumps. A 6 to 8 mesh fraction was used as a catalyst. The same method of testing was used as in Example 1 with the same fiow rates of reactants being employed. At a maximum temperature in the reactor of 650 C., the yield of butadiene per pass was greater than mol percent.

Example 3 A cobalt ferrite catalyst was formed in the following manner: 119.0 grams of cobaltous chloride and 135.2 grams of ferric chloride were dissolved in 500 cc. of distilled water. A second solution was prepared by dissolving grams of sodium hydroxide in one liter of distilled water. The mixed chloride solution was added slowly to the sodium hydroxide solution with stirring. A coprecipitate and cobaltous and ferric hydroxides was obtained. The slurry was then dewatered by filtering and washed with distilled water until it was neutral. The mixture was dried in an oven at a temperature of 110 C, After drying, the black solid was reacted in a furnace at a temperature of 900 C. for a period of one andone-half hours. Cobalt ferrite, magnetic black solid, was obtained. Butene-2 was dehydrogenated to butadiene-l,3. Oxygen was fed in an amount of 0.6 mol per mol of butene-2 and steam was utilized in an amount of 30 mols per mol of butene-2. The liquid hourly space velocity was 1.0. At a reactor temperature of 540 C., the butene-2 was converted to butadiene-1,3 at a high selectivity.

Example 4 The procedure of Example 3 was repeated with the exception that the cadmium ferrite catalyst utilized in Example 1 was used instead of the cobalt ferrite catalyst of Example 3. At a maximum temperature in the reactor of 500 C., butene was dehydrogenated to butadiene-l,3 at a selectivity of greater than 80 mol percent.

Example Example 3 was repeated with the exception that the calcium ferrite catalyst of Example 2 was used instead of the cobalt ferrite catalyst of Example 3. Butene-2 was dehydrogenated to butadiene-1,3 at a reactor temperature of 600 C.

When HI or HCl was substituted for HBr in the above Examples 1 and 2, high yields of butadiene-1,3 were obtained.

We claim:

1. A process for the dehydrogenation of aliphatic hydrocarbons having at least four carbon atoms which comprises contacting in the vapor phase at a temperature of greater than 250 C. a mixture of the said hydrocarbon to be dehydrogenated and from 0.2 to 2.5 mols of oxygen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon.

2. A process for the dehydrogenation of hydrocarbons from 4 to 5 carbon atoms which comprises contacting in the vapor phase at a temperature of greater than 250 C. a mixture of the said hydrocarbon to be dehydrogenated and from 0.2 to 2.5 mols of oxygen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite wherein the atoms of iron are present in an amount of about to 90 weight percent based on the total weight of the atoms of iron and the element selected from the group consisting of calcium, cobalt and cadmium, to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than one-half atmosphere at a total pressure of one atmosphere.

3. A process for the dehydrogenation of a hydrocarbon selected from the group consisting of n-butene, n-butane and mixtures thereof which comprises contacting in the vapor phase at a temperature of greater than about 325 C. a mixture of the said hydrocarbon to be dehydrogenated and from about 0.25 to about 1.6 mols of oxygen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than one-half atmosphere at a total pressure of one atmosphere.

4. A process for the dehydrogenation of aliphatic hydrocarbons having at least four carbon atoms which comprises contacting in the vapor phase at a temperature of greater than 325 C. a mixture of the said hydrocarbon to be dehydrogenated from 0.2 to 2.5 mols of oxygen per mol of the said hydrocarbon and from 2 to mols of steam per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon.

-5. A process for the dehydrogenation of hydrocarbons having from 4 to 5 carbon atoms which comprises contacting in the vapor phase at a temperature of at least about 375 C. a mixture of the said hydrocarbon to be dehydrogenated and from 0.35 to 1.2 mols of oxygen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite wherein the atoms of iron are present in an amount of 55 to 79 weight percent based on the total weight of the atoms of iron and the element selected from the group consisting of calcium, cobalt and cadmium, to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than one-third atmosphere at a total pressure of one atmosphere.

6. A process for the dehydrogenation of a hydrocarbon selected from the group consisting of n-butene, nbutane and mixtures thereof which comprises contacting in the vapor phase at a temperature of from 375 C. to 525 C. and at a pressure of 4 p.s.i.a. to 125 p.s.i.a. a mixture of the said hydrocarbon to be dehydrogenated and from about 0.25 to about 1.6 mols of oxygen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than onefifth atmosphere at a total pressure of one atmosphere.

7. A process for the dehydrogenation of butene to butadiene-l,3 which comprises contacting in the vapor phase at a temperature of from 375 C. to 575 C. and at a total pressure of less than p.s.i.a. a mixture of the said butene, from 8 to about 35 mols of steam and from 0.35 to 1.2 mols of oxygen per mol of the said butene with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite wherein the atoms of iron are present in an amount of 50 to 79 weight percent based on the total weight of the atoms of iron and the element selected from the group consisting of calcium, cobalt and cadmium to produce butadiene-l,3.

8. A process for the vapor phase dehydrogenation of aliphatic hydrocarbons having at least four carbon atoms which comprises contacting in the vapor phase at a temperature of greater than 250 C. a mixture of the said hydrocarbon to be dehydrogenated, from 0.2 to 2.5 mols of oxygen per mol of the said hydrocarbon and a halogen with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite wherein the atoms of iron are present in an amount of about 40 to weight percent based on the total Weight of the atoms of iron and the element selected from the group consisting of calcium, cobalt and cadmium to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than one-half atmosphere at a total pressure of one atmosphere.

9. A process for the dehydrogenation of aliphatic hydrocarbons having from 4 to 5 carbon atoms which comprises contacting in the vapor phase at a temperature of greater than 325 C. a mixture of the said hydrocarbon to be dehydrogenated, from 0.25 to 1.6 mols of oxygen per mol of the said hydrocarbon and from 0.0001 to 0.2 mol of halogen per mol of the said hydrocarbon with an autoregenerative catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite wherein the atoms of iron are present in an amount of about 40 to 85 weight percent based on the total weight of the atoms of iron and the element selected from the group consisting of calcium, cobalt and cadmium to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than one-half atmosphere at a total pressure of one atmosphere.

10. A process for the dehydrogenation of aliphatic hydrocarbons having from 4 to 5 carbon atoms which comprises contacting in the vapor phase at a temperature of greater than 325 C. a mixture of the said hydrocarbon to be dehydrogenated, from 0.25 to 1.6 mols of oxygen per mol of the said hydrocarbon and from 0.0001 to 0.2 mol of bromine per mol of the said hydrocarbon with an autoregenerative catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite wherein the atoms of iron are present in an amount of about 40 to 85 weight percent based on the total Weight of the atoms of iron and the element selected from the group consisting of calcium, cobalt and cadmium, to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than one-half atmosphere at a total pressure of one atmosphere.

11. A process for the dehydrogenation of a hydrocarbon selected from the group consisting of n-butene, nbutane and mixtures thereof which comprises contacting in the vapor phase at a temperature of greater than about 325 C. a mixture of the said hydrocarbon to be dehydrogenated and from about 0.25 to about 1.6 mols ofoxygen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising calcium ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the said catalytic surface having X-ray diifraction peaks at d spacings within the ranges of about 2.64 to 2.68, 2.50 to 2.54, and 1.49 to 1.53, with the most intense peak being between about 2.64 to 2.68.

12.. A process for the dehydrogenation of a hydrocarbon selected from the group consisting of n-butene, n-butane and mixtures thereof which comprises contacting in the vapor phase at a temperature of greater than about 325 C. a mixture of the said hydrocarbon to be dehydrogenated and from about 0.25 to about 1.6 mols of oxygen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising cobalt ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the said catalytic surface having X-ray diffraction peaks at d spacings within the ranges of about 2.51 to 2.56, 1.46 to 1.50 and 1.59 to 1.63 with the most intense peak being between about 2.51 to 2.56.

13. A process for the dehydrogenation of a hydrocarbon selected from the group consisting of n-butene, nbutane and mixtures thereof which comprises contacting in the vapor phase at a temperature of greater than about 325 C. a mixture of the said hydrocarbon to be dehydrogenated and from about 0.25 to about 1.6 mols of oxygen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising cadmium ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the said catalytic surface having X-ray diffraction peaks at d spacings within the ranges of about 2.59 to 2.64, 3.05 to 3.09 and 1.65 to 1.69 with the most intense peaks being between about 2.59 to 2.64.

14. A process for the dehydrogenation of aliphatic hydrocarbons having at least four carbon atoms which comprises contacting in the vapor phase at a temperature of greater than 250 C. a mixture of the said hydrocarbon to be dehydrogenated and from 0.2 to 2.5 mols of oxygen per mol of the said hydrocarbon with a catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite to produce a dehydrogenated hydrocarbon product having the same number of carbon atoms as the said hydrocarbon, the initial partial pressure of the said hydrocarbon being equivalent to less than one-half atmosphere at a total pressure of one atmosphere, said catalyst having been reduced with a reducing gas.

15. A process for the preparation of butadiene-1,3 which comprises contacting in the vapor phase at a temperature of 375 C. to 525 C. and at a total pressure of about 4 p.s.i.a. to p.s.i.a. a mixture of n-butene and from 0.35 to 1.2 mols of oxygen and from 8 to 35 mols of steam per mol of the said n-butene with an autoregenerative catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite wherein the atoms of iron are present in an amount of about 2 atoms of iron per atom of the element selected from the group consisting of calcium, cobalt and cadmium, with any iron not present in the form of the ferrite being predominantly present as gamma iron oxide, to produce butadine-1,3.

16. A process for the preparation of butadine-1,3 which comprises contacting in the vapor phase at a temperature of 375 C. to 525 C. and at a total pressure of about 4 p.s.i.a. to 100 p.s.i.a. a mixture of n-butene and from 0.35 to 1.2 mols of oxygen and from 8 to 35 mols of steam per mol of the said n-butene with an autoregenerative catalyst for the dehydrogenation comprising a ferrite selected from the group consisting of calcium ferrite, cobalt ferrite and cadmium ferrite with any iron not present in the form of the ferrite being predominantly present as gamma iron oxide to produce butadiene-1,3, and after the yield of butadiene-1,3 has fallen off after continued use regenerating the catalyst by reducing the catalyst with hydrogen References Cited UNITED STATES PATENTS 3,168,587 2/1965 Michaels et a1. 2606833 3,179,707 4/1965 Lee 260-669' 3,207,811 9/1965 Bajars 260680 DELBERT E. GANTZ, Primary Examiner.

G. E. SCHMITKONS, Assistant Examiner. 

1. A PROCESS FOR THE DEHYDROGENATION OF ALPHATIC HYDROCARBONS HAVING AT LEAST FOUR CARBON ATOMS WHICH COMPRISES CONTACTING IN THE VAPOR PHASE AT A TEMPERATURE OF GREATER THAN 250*C. A MIXTURE OF THE SAID HYDROCARBON TO BE DEHYDROGENATED AND FROM 0.2 TO 2.5 MOLS OF OXYGEN PER MOL OF THE SAID HYDROCARBON WITH A CATALYST FOR THE DEHYDROGENATION COMPRISING A FERRITE SELECTED FROM THE GROUP CONSISTING OF CALCIUM FERRITE, COBALT FERRITE AND CADMIUM FERRITE TO PRODUCE A DEHYDROGENATED HYDROCARBON PRODUCT HAVING THE SAME NUMBER OF CARBON ATOMS TO THE SAID HYDROCARBON. 